Sedimentation is one of the consequences of hydropower plant construction. Such structures not only have an influence on reservoir morphology, but also have great impact on both upstream and downstream river morphology. This study focuses on fluvial morphological changes in between two hydropower plants on the Drava River, Austria. The influence of both reservoir management methods (flushing) and human intervention (groynes) have been investigated. The first stage started with validating an unsteady Delft3D morphodynamic model of the meandering reach. This validation shows the importance of spatial grain size distribution in predicting bed load transport. Analysis of the flushing method includes investigation of the duration of gate-opening before and after peak flood. The results show that the duration of lowering the water level at the hydropower plant (by opening the gate) before starting the peak flood will not have a big influence on the river morphology upstream of the reservoir. However, the duration of maintaining the low water level after the peak flood has a large influence on both the river morphology in the upstream portion of the reservoir and on the sediment transport toward the reservoir In the second part of this study, hydraulic structural groynes were applied in the river reach. The objective was to design a groyne field that will minimize sediment transport to the reservoir. Both emerged and submerged groynes were investigated. In addition, the influences of both groyne head shape and the distribution of sediment grain size in the groyne zone were examined. This study shows that under an unsteady simulation, when the groynes are submerged by 1m at normal flow, the sediment supply to the groyne zone decreases compared to the emerged case. However, if the groynes are submerged by 0.5m, the sediment supply to the groyne zone will be greater than the emerged case for an aspect ratio in between (0.5-2). Finally, applying L-head groynes produces less erosion in the main stream and a higher sediment supply compared to straight groynes.

Deltas are important coastal systems throughout the world. River mouth bars are key landforms in the development of deltas, are characterized by sediment deposition, and have high potential for sediment preservation. Scientists and professionals seek to understand the discrete response of mouth bars to the various controls governing their evolution. This study utilizes the numerical modelling software Delft3D to provide additional evidence supporting the morphological and stratigraphic responses resulting from variations in basin configurations and allogenic controls (fluvial discharge, tides, basin width). Mud content within the bar increased analogous to an increase in the tidal modulation, while a decrease in the initial basin depth reduced mud content. Initial basin slope and lateral confinement had less obvious impacts on stratigraphy. Finally, variable fluvial discharge and the incorporation of realistic tidal harmonics produced similar bar morphologies (compared to simulations with constant flow and sinusoidal tides), yet demonstrated significant differences in bar stratigraphy.

As the forecasting models become more sophisticated in their physics and possible depictions of the nearshore hydrodynamics, they also become increasingly sensitive to errors in the inputs. These input errors include: mis-specification of the input parameters (bottom friction, eddy viscosity, etc.); errors in input fields and errors in the specification of boundary information (lateral boundary conditions, etc.). Errors in input parameters can be addressed with fairly straightforward parameter estimation techniques, while errors in input fields can be somewhat ameliorated by physical linkage between the scales of the bathymetric information and the associated model response. Evaluation of the errors on the boundary is less straightforward, and is the subject of this thesis. The model under investigation herein is the Delft3D modeling suite, developed at Deltares (formerly Delft Hydraulics) in Delft, the Netherlands. Coupling of the wave (SWAN) and hydrodynamic (FLOW) model requires care at the lateral boundaries in order to balance run time and error growth. To this extent, we use perturbation method and spatio-temporal analysis method such as Empirical Orthogonal Function (EOF) analysis to determine the various scales of motion in the flow field and the extent of their response to imposed boundary errors. From the Swirl Strength examinations, we find that the higher EOF modes are affected more by the lateral boundary errors than the lower ones.

Made available in DSpace on 2018-08-24T22:53:33Z (GMT). No. of bitstreams: 1 tese_7562_dissertacao_fernando.pdf: 3574819 bytes, checksum: 38a5c68024b79a747d1a0f514e27bfba (MD5) Previous issue date: 2014-02-24 / O cisalhamento resultante da interação entre a Corrente do Brasil (CB) e a Corrente de Contorno Intermediária (CCI) é um dos principais fatores responsáveis por importantes feições encontradas ao largo da costa do Espírito Santo-Brasil, como vórtices e meandramentos. Apesar disso, existem poucos estudos mostrando a influência do sistema CB/CCI na dinâmica de mesoescala dessa região, que é de importância crucial para o país devido ao seu potencial petrolífero. Assim, neste trabalho foram realizados experimentos de sensibilidade através do modelo Delft3D, onde foram variadas as velocidades da CB e da CCI, com o intuito de se estudar o campo de escoamento resultante dessa variação, e com isso ajudar na compreensão da dinâmica de mesoescala da região oceânica adjacente ao ES. Para isso foram analisados seções verticais de velocidade, a intrusão de água fria de regiões mais profundas sobre a plataforma, o Vórtice de Tubarão (VT) e o Vórtice Ciclônico de Tubarão (VCT). Os resultados mostraram que a variação da velocidade das correntes induziu uma modificação da extensão vertical dessas e uma translação longitudinal de seus núcleos, sendo isto responsável pela variação da intrusão de uma água mais fria sobre a plataforma continental observada nos experimentos. Em relação aos vórtices, foi encontrado uma dominância da dinâmica do Vórtice de Tubarão pela CB, enquanto modificações da velocidade tanto da CB quanto da CCI induziram significativas modificações no Vórtice Ciclônico de Tubarão. Esta diferença entre o VT e o VCT está provavelmente relacionada às diferenças na extensão vertical dos dois vórtices. Enquanto foi identificado o sinal do VT apenas na CB, o do VCT foi identificado na CB e na CCI. No final do trabalho concluiu-se que as variações da velocidade não foram capazes de modificar o cenário de mesoescala na região, como ocorreu em Soutelino et al. (2013) para os seus experimentos de sensibilidade.

Dissertação(mestrado)-Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2003. / Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-23T19:48:22Z No. of bitstreams: 1 Processo que regem a qualidade da água da Lagoa dos. Patos, segundo o modelo Delft3D.pdf: 1880851 bytes, checksum: 0fe34fc0976536f35ac95f7d91ff25a7 (MD5) / Approved for entry into archive by Gabriela Silva da Rosa(gabrielasilvadarosa@gmail.com) on 2013-07-01T21:17:40Z (GMT) No. of bitstreams: 1 Processo que regem a qualidade da água da Lagoa dos. Patos, segundo o modelo Delft3D.pdf: 1880851 bytes, checksum: 0fe34fc0976536f35ac95f7d91ff25a7 (MD5) / Made available in DSpace on 2013-07-01T21:17:40Z (GMT). No. of bitstreams: 1 Processo que regem a qualidade da água da Lagoa dos. Patos, segundo o modelo Delft3D.pdf: 1880851 bytes, checksum: 0fe34fc0976536f35ac95f7d91ff25a7 (MD5) Previous issue date: 2003 / Os modelos numéricos se propõem a simular tanto os processos de transporte como os processos químicos que ocorrem num corpo hídrico. O objetivo deste trabalho é avaliar os processos que determinam a qualidade das águas da Lagoa dos P atos, utilizando pela primeira vez o modelo Delft3D da WL | Delft Hydraulics. Neste modelo foram aplicados os dados obtidos no Programa para o Desenvolvimento Racional, Recuperação e Gerenciamento Ambiental da Lagoa dos Patos/Mirim – Pró Mar de Dentro, que realizou onze cruzeiros de amostragem, durante o período compreendido entre fevereiro de 1999 e janeiro de 2000. A primeira etapa realizada foi a validação do modelo hidrodinâmico, que foi feita comparando-se os dados de salinidade obtidos em campo ao longo da Lagoa com os resultados das simulações. Em seguida, com o modelo hidrodinâmico validado, foi aplicado o modelo de qualidade de água. Os seguintes parâmetros foram avaliados: material em suspensão, oxigênio dissolvido, DBO, nitrato, nitrito, amônio, nitrogênio total, fosfato, fósforo total, carbono orgânico total, sílica, cromo, cobre, zinco, chumbo, níquel, cádmio, ferro. Os resultados mostraram que o modelo foi validado, apresentando bons resultados na simulação da circulação da Lagoa dos Patos. Apesar de alguns desvios terem sido percebidos, não se deveram propriamente ao modelo e sim a ausência de uma melhor distribuição temporal e espacial de dados para alimentá-lo. A avaliação dos parâmetros de qualidade de água indicou que os processos químicos e físicos que ocorrem na Lagoa variam espacialmente e temporalmente, dependendo principalmente das condições metereológicas da região. Apesar das diversas influências antrópicas presentes na Lagoa dos Patos, as águas do eixo principal da Lagoa não apresentaram sérias contaminações que tragam riscos aos ecossistemas que a cercam e dela dependem. De acordo com os resultados obtidos, o modelo poderia tornar-se uma importante ferramenta na previsão e avaliação da qualidade da água da Lagoa dos Patos. / Numeric models intend to simulate both the transport and chemical processes that happen in a water body. The aim of this work is to evaluate the processes that govern the quality of the Patos Lagoon water, using for the first time Delft3D model, from WL | Delft Hydraulics. The model was applied using data obtained during the project denominated “Programa para o Desenvolvimento Racional, Recuperação e Gerenciamento Ambiental da Lagoa dos Patos/Mirim – Pró Mar de Dentro”, wich carried out eleven sampling campaigns, during the period of February 1999 and January 2000. First stage, consisted hydrodynamic model validation, that was made comparing the salinity data obtained during the samplig with the simulations results. Second stage, with the hydrodynamic model validated, the water quality model was applied. The following parameters were evaluated: suspended matter, dissolved oxygen, BOD, nitrate, nitrito, ammonium, total nitrogen, phosphate, total phosphorous, total organic carbon, silicate, chromium, copper, zinc, lead, nickel, cadmium, iron. The results showed that the model was validated, presenting good results in the circulation simulation of the Patos Lagoon. In spite of some deviations have been observed, they were not due properly to the model, but due the absence of more precise data for apply in the model. The evaluation of the water quality parameters indicated that chemical and physical processes that happen in the Lagoon have variation in the space and in the time, mainly depending on the metereological conditions of the region. In spite of several antropogenics influences present in the Patos Lagoon, waters in your main axis didn't present contaminations that bring risks to the survival of the ecossystems that surround and depend on this Lagoon. According to the obtained results, the model could become an important tool in the forecast and evaluation of the water quality of the Patos Lagoon.

The study of fluvial geomorphology is one of the critical sciences in the 21st Century. The previous century witnessed a virtual disregard of the hydro and morphodynamic processes occurring in rivers when it came to design of transportation, flood control, and water resources infrastructure. This disregard, along with urbanization, industrialization, and other land uses has imperiled many waterways. New technologies including geospatially referenced data collection, laser-based measurement tools, and increasing computational powers by personal computers are significantly improving our ability to represent these complex and diverse systems. We can accomplish this through both the building of more sophisticated models and our ability to calibrate those models with more detailed data sets. The effort put forth in this dissertation is to first introduce the accomplishments and challenges in fluvial geomorphology and then to illustrate two specific efforts to add to the growing body of knowledge in this exciting field.First, we explore a dramatic phenomenon occurring in the Middle Rio Grande River. The San Marcial Reach of the Rio Grande River has experienced four events that completely filled the main channel with sediment over the past 20 years. This sediment plug has cost the nation millions of dollars in both costs to dredge and rebuild main channels and levees, along with detailed studies by engineering consultants. Previous efforts focused on empirical relations developed with historical data and very simple one dimensional representation of river hydrodynamics. This effort uses the state-of-the-art three-dimensional hydro and morphodynamic model Delft3D. We were able to use this model8to test those hypotheses put forth in previous empirical studies. We were also able to use this model to test theories associated with channel avulsion. Testing found that channel avulsions thresholds do exist and can be predicted based on channel bathymetric changes.The second effort included is a simple yet sophisticated model of river meander evolution. Prediction of river meandering planform evolution has proven to be one of the most difficult problems in all of geosciences. The limitations of using detailed three dimensional hydro and morphodynamic models is that the computational intensity precludes the modeling of large spatial or temporal scale phenomenon. Therefore, analytical solutions to the standard Navier-Stokes equations with simplifications made for hydrostatic pressure among others, along with sediment transport functions still have a place in our toolbox to understand and predict this phenomenon. One of the most widely used models of meander propagation is the Linear Bend Model that employs a bank erosion coefficient. Due to the various simplifications required to find analytical solutions to these sets of equations, efforts to build the stochasticity seen in nature into the models have proven useful and successful. This effort builds upon this commonly used meander propogation model by introducing stochasticity to the known variability in outer bank erodibility, resulting in a more realistic representation of model results.

Thesis advisor: Douglas Edmonds / Due to their low-lying position near the shoreline, river deltas are vulnerable to fluctuations in relative sea-level (RSL). Moreover, relatively little is known about fluvio-deltaic dynamics during RSL fall because the resulting deposits have low preservation potential. In this paper, I present a field-based study of the Goose River delta, coupled with numerical model simulations, that investigates the fluvio-deltaic response to RSL fall. The Goose River delta is a sandy fjord delta at the mouth of the Goose River located at the western end of Lake Melville, an inlet of the Labrador Sea, Canada and has experienced a RSL fall of 3 to 6 mm/yr in the past 5000 years due to post-glacial isostatic rebound. Aerial images show three abandoned delta lobes and one active lobe, suggesting that avulsions and lobe-switching occurred during RSL fall. Elevation analysis using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data and optically-stimulated luminescence (OSL) dating suggest that a series of downstepping terraced delta lobes formed at the mouth of the Goose River during a period of RSL fall. Similarly, Delft3D model runs show continued avulsions and formation of multiple terraced delta lobes deposited at progressively lower elevations. I show computationally that by decreasing delta lobe widths, deltas may remain aggradational during RSL fall, creating conditions favorable for lobe-switching during RSL fall. Observations from the field and model runs provide a critical link in understanding the geomorphic processes occurring during RSL fall, and in particular show that 1) incision and sediment bypass is not a necessary response to RSL fall and 2) lateral migration of a delta via avulsion can continue to occur with falling sea-level. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Total suspended matter (TSM) concentrations were derived from ocean colour imagery (MERIS data) in Minas Basin. Analysis of time series of TSM in 1-km2 pixel boxes throughout the Basin revealed an annual cycle in TSM in most parts of the Basin. Higher TSM of up to 85 g/m3 was observed in late-winter (February - March), and lower TSM of 5-10 g/m3 characterized late-summer (July - August). The largest annual variation occurred in the centre of Basin, and the smallest variation occurred in shallow areas. Satellite-derived TSM were compared to predictions using the Delft3D model. Increasing model erosion rate in winter relative to summer was necessary to improve agreement between model and satellite-derived TSM. In comparison with the satellite-derived estimates, the model underestimated TSM in shallow areas in summer and overestimated it in winter. This discrepancy is likely due to inaccurate satellite-derived TSM in shallow, high concentration areas of the Basin.

The exchange of dissolved constituents between a shallow bay and the ocean is governed by regular tidal fluxes as well as by wind generated storm surges and currents. In this study the transport of a conservative tracer was simulated using the numerical model Delft3D in a system of shallow bays along the coast of the Delmarva Peninsula, Virginia. The evaluation of the tracer residence time was carried out using the Eulerian approach. The main mechanisms governing the decay of the tracer concentration inside the lagoons were assessed by considering the influence of different factors such as the time of release of the tracer with respect to the tidal cycle, tidal amplitude, and local winds. The exponential curve well approximates the decay of the tracer concentration in time. A set of simulations shows that the prevailing factor controlling the tracer transport and, therefore, the tracer concentration within the lagoons are wind-driven fluxes. Large tidal amplitudes also promote the flushing of the tracer out of the bay, while the time of tracer release with respect to the tidal phase has been found to play a relatively negligible role. Finally, a simplified approach is presented to compute the decay of tracer concentration in time. The method accounts for hourly variable wind characteristics as well as seasonal changes in meteorological conditions.

To accommodate an increasing number of tourists visiting Bequia, the second largest island of Saint-Vincent and the Grenadines, the local government constructed an airport, through a major coastline land-reclamation project. However, due to the prevailing ocean current patterns in the area, an inlet created on the east side of the new airport is prone to trapping significant amounts of ocean-borne debris. This litter accumulation creates a health risk to local fishermen who clean their daily catch using water from the inlet. It is proposed to install a rubble-mound groyne structure on the eastward side of the new inlet to address this problem. The utilisation of a coastline groyne in this case is somewhat unorthodox, as the latter is normally employed to mitigate against coastal erosion. The goal of this study is to optimise the groyne design with the assistance of a 3D numerical model. The ‘Delft3D’ open-source model (WAVE and FLOW modules) was selected to examine the effects of different orientations and lengths of the proposed groyne on the movements of floating debris. Included in the initial phase of the study was a field investigation to collect certain data which were necessary for model calibration and validation. This involves the use of an Acoustic Doppler Current Profiler (ADCP) to measure local shore bathymetry and also current velocities over a range of tidal cycles.